“Wireless computing” is a term that has come to describe wireless communications between computing devices or between a computer and peripheral devices such as printers. For example, many computers, including tower and laptop models, have a wireless communications card that comprises a transmitter and receiver connected to an antenna. Or alternatively, a Host Wire Adapter (HWA) is connected to the computer by a USB (Universal Serial Bus) cable. The HWA has an RF (Radio Frequency) transmitter and receiver capable of communicating data in a USB-cognizable format. This enables the computer to communicate by RF transmission with a wireless network of computers and peripheral devices. The flexibility and mobility that wireless computing affords is a major reason for its commercial success.
An antenna used for wireless applications must typically be able to transmit to and receive from a variety of devices in different locations. Using state of the art technology for fabrication of antenna arrays, lenses, and reflectors, as well as semiconductor components, it is possible to fabricate inexpensive antenna systems with beam-switching capability that operate in the milli-meter (mm)-wave frequency band exhibiting shorter wavelengths. It is well known that the shorter wavelength of transmission, the higher the attenuation experienced by electromagnetic waves during propagation. Thus, propagating mm-waves suffer from very strong attenuation. Other factors such as oxygen absorption further worsen the situation making the attenuation even higher.
At mm-wave frequencies it is difficult or impossible to extend communication range by increasing transmitted power, because of difficulties implementing high power semiconductor transmitters, and because of FCC (Federal Communications Commission) limitations imposed on transmitted power. Sufficiently long communication distances can be achieved using high gain directive antennas. However, high-gain antennas have narrow beam-widths, so there is a problem of antenna alignment and accurate pointing to effectuate communication with a peripheral device. To solve the problem of antenna beam pointing, beam controlled antennas are required. Steerable beam or beam switched high-gain antennas will allow communication at sufficiently long distances and are needed for the next generation of WPAN (Wireless Personal Area Network) and WLAN (Wireless Local Area Network) mm-wave communication equipment. Traditionally, internal switching of radiators in an antenna array (for the purpose of beam direction control) is based on RF semiconductor switches, incorporated into the signal distribution circuit. A low loss and low cost signal distribution circuit required for switching of radiators is very difficult to implement at mm-wave frequencies. Thus, another method of beam steering is needed.